The invention relates to a circuit configuration for a serial communication with wake up function and relates to, in particular, a circuit configuration without a quiescent current for a serial interface with bidirectional wake up function in a motor vehicle.
If a motor vehicle has electronic control units, intelligent sensors and actuators for sensing and controlling the operation of the vehicle, a wake up function is often provided in cases, in which the whole system is inactive or is in a standby mode, in order to be able to shift the involved subsystems out of their respective standby mode back again into a state of being ready for service. For such applications predominantly a LIN (local interconnect network) or a K line and/or a diagnostic interface with an awakening function, that is a wake up function, is used. These interfaces are the communication standards based on ISO standard 9141, where the communication is based on a bit serial single wire line in accordance with the SCI (UART) data format, and the maximum transfer rate is 20 Kbit/s.
The drawback with the aforementioned interfaces is, on the one hand, their implementation costs because of a certain complexity, for example, in the protocol based LIN interface that requires a driver, and, on the other hand, the constantly necessary quiescent current even in the off state, especially for the wake up function. This quiescent current has to be supplied continuously, in order to guarantee the wake up function, and, therefore, constitutes a load on the electrical system of the vehicle both with respect to the strain on the installed components and with respect to a lower reliable operational readiness of, for example, the parked vehicle.
Therefore, the object of the invention is to provide an inexpensive serial communication over an interface between a sensor and/or actuator subsystem and a central electronic control unit that makes a wake up function without quiescent current ready for use in a bidirectional manner.
The invention is based on providing an inexpensive serial communication between a sensor/actuator configuration and an electronic control unit at a transfer rate of up to 20 Kbit/s. The communication is able to wake up bidirectionally by providing a wake up switching device, which on the side of the sensor/actuator configuration shifts the sensor/actuator configuration out of a standby state without a quiescent current by connecting it to the supply voltage. This connection is communicated over a two wire line to the control unit, which in turn also leaves its standby mode. This departure of the control unit from its standby mode is then communicated to the sensor/actuator configuration over the two wire line, so that at this time a self-holding of the supply voltage is achieved by holding the respective states of the supply voltage switches independently of the position of the wake up switching device.
Thus, this object of the invention is achieved by a circuit configuration for a serial communication, characterized by: (a) a first half of the circuit configuration for receiving and emitting sensing and/or actuating signals; (b) a second half of the circuit configuration for receiving and emitting sensing and/or actuating signals; (c) a two wire connecting line, which connects bidirectionally the first half of the circuit configuration and the second half of the circuit configuration; and (d) a wake up switching device for waking up the first half of the circuit configuration and the second half of the circuit configuration out of their standby mode without quiescent current.
Preferably, the first half of the circuit configuration includes a first switching device for switching a supply voltage of the first half of the circuit configuration, a first signal shaping device, which is connected to the first switching device and is intended for shaping a signal on a data receiving line of the first half of the circuit configuration, a first transistor device, which is connected to the first signal shaping device and which is intended for controlling a data communication on a data transmission line of the first half of the circuit configuration, a first low pass filter device, which is disposed in the data transmission line of the first half of the circuit configuration, and the wake up switching device.
In an especially preferred embodiment, the second half of the circuit configuration includes a second switching device for switching a supply voltage of the second half of the circuit configuration, a second signal shaping device, which is connected to the second switching device and is intended for shaping a signal on a data receiving line of the second half of the circuit configuration, a second transistor device, which is connected to the second switching device and which is intended for controlling a data communication on a data transmission line of the second half of the circuit configuration, and a second low pass filter device, which is disposed in the data transmission line of the second half of the circuit configuration.
In addition, the wake up switching device for waking up the first and the second half of the circuit configuration is designed preferably to shift the first switching device into a closing state.
Preferably, the result of shifting the first switching device into the closing state is that the first transistor device is supplied with an operating voltage, and an output of the first low pass filter device assumes a level in such a manner that the second switching device is shifted into a closing state. Preferably the result of shifting the second switching device is that the second transistor device is supplied with the operating voltage, and an output of the second low pass filter device assumes a level in such a manner that the first switching device stays in its closing state, independently of a switching state of the wake up switching device.
The first half of the circuit configuration is advantageously a sensor device, an actuator device or a sensor/actuator device.
In an additional advantageous design the second half of the circuit configuration is a central electronic control unit.
In an even more advantageous design, the first half of the circuit configuration is a part of a foot brake module of an electronic brake system in a motor vehicle, and the second half of the circuit configuration is a central electronic control unit of the electronic brake system in the motor vehicle.
The first half and the second half of the circuit configuration are also preferably digital circuit configurations, and the first and the second switching device are electronic switches.
The object of the invention is achieved with a method for waking up from a standby mode without quiescent current a first half of the circuit configuration and a second half of the circuit configuration, which are connected by way of the communication lines and which form a bidirectional full duplex communication interface with a transfer rate of up to 20 Kbit/s, by means of a wake up switching device, characterized by the steps: (a) shifting the wake up switching device into a closing state, (b) shifting a first switching device in the first half of the circuit configuration into a closing state, (c) supplying a first transistor device with an operating voltage, (d) shifting an output of a first low pass filter device into a high level state, (e) shifting a second switching device in the second half of the circuit configuration into a closing state, (f) supplying a second transistor device with an operating voltage, and (g) shifting an output of a second low pass filter device into a high level state; wherein then independently of the switching state of the wake up switching device, the high level state at the output of the second low pass filter device holds the switching device in its closing state, and the high level state at the output of the first low pass filter device holds the second switching device in its closing state.
The invention is described in detail below by means of one preferred embodiment with reference to the drawing.